A pellicle is used so as to prevent dust particles from depositing on a photomask or a reticle (hereinafter they will be referred to as a mask pattern surface) used in photolithography (exposure treatment) as a step in production of semiconductor devices or liquid crystal display panels. A pellicle is an optical article comprising a transparent thin membrane (hereinafter referred to as a pellicle membrane) bonded to a frame by means of an adhesive, to be mounted on the mask pattern at some distance from the mask surface. A pellicle is required to have transparency to a light to be used for the exposure treatment, durability and mechanical strength.
In production of semiconductor devices and liquid crystal display panels, minimization of wiring and wiring interval is in progress. For wiring processing with a minimum pattern dimension of at most 0.3 μm, a KrF excimer laser having an irradiation wavelength of 248 nm is used as a light source for the exposure treatment. As a material of a pellicle in the exposure treatment, a fluoropolymer having a saturated cyclic structure in its main chain has been known (Patent Documents 1 and 2).
In recent years, wiring processing with a minimum pattern dimension of at most 0.2 μm has been required, and it has been studied to use, as a light source for the exposure treatment, an excimer laser having an irradiation wavelength of at most 200 nm (such as an ArF excimer laser light having an irradiation wavelength of 193 nm or a F2 excimer laser light having an irradiation wavelength of 157 nm). Particularly for wiring processing with a minimum pattern dimension of at most 0.07 μm, a F2 excimer laser light is considered to be most promising, but the above fluoropolymer has no sufficient transparency and durability thereto. Also the adhesive to fix the pellicle membrane to the frame has had a similar problem due to reflected light or scattering light of the laser light.
Further, as another pellicle material, (1) a fluororesin having an ether bond at a moiety forming the main chain in the repeating structure and containing no cyclic structure (Patent Document 3) and (2) a substantially linear fluoropolymer comprising as the main chain a chain of carbon atoms (Patent Document 4) have been proposed.
Patent Document 1: JP-A-3-39963
Patent Document 2: JP-A-3-67262
Patent Document 3: JP-A-2001-255643
Patent Document 4: JP-A-2001-330943